The invention relates to a method and apparatus for the consumption-oriented driving-power limitation of a vehicle drive, and to a device for driving-power limitation. The method according to the invention can be applied to vehicles of all kinds on water, on land and in the air, which carry an energy accumulator for the provision of the driving energy, especially electric vehicles with traction batteries.
German patent document DE 30 01 470 C2 discloses a travelling-data computer with an associated indicator for motor vehicles, by means of which current information, such as, for example, instantaneous operating parameter values of the vehicle, and information determined from such parameter values and from values input by the driver, can be called up as required. Thus, for example, it should be possible to call up the available travelling range remaining on the basis of the instantaneous content of the fuel tank, the instantaneous fuel consumption and an average fuel consumption derived therefrom. Similarly, by inputting the stretch of road ahead (distance) and the desired arrival time, the computer should calculate the nominal speed to be maintained, and display it. A speed limit value can also be input, so that reaching or exceeding the limit may be indicated by an acoustic or optical signal.
With the indication of the range and the speed limiter, the known travelling-data computer gives the driver only a rough guide in the allocation of the existing fuel supply. For motor vehicles with an internal combustion engine, this is not critical, since there is generally a relatively dense network of filling stations available.
However, this is not the case for electric vehicles operated with a battery. It is absolutely essential that the vehicle should not inadvertently be stuck en route, because the network of recharging stations is not yet very extensive relative to currently possible driving ranges. Since, moreover, a recharging operation can be very time-consuming, it may be worthwhile, by a deliberately restrained manner of driving, to allocate the existing energy supply in such a way that it is just sufficient to reach the destination.
It is an object of the present invention to provide a method and apparatus to assist the vehicle user in reaching his destination as rapidly as possible using a given energy supply in a substantially optimum and economical manner.
This object is achieved according to the invention, based on the recognition that the range of vehicles with on-board energy accumulators falls drastically as the travelling speed increases. This is attributable, on the one hand, to the increase in travelling resistance with travelling speed and, on the other hand, to the poorer efficiency of the prime movers and many energy accumulators in the upper power range. Particularly in the case of electric energy accumulators, the resistance losses increase with the power demand. By controlling the driving power, especially by specifying a guideline speed determined by the computer as a function of the stretch of road to be travelled, the method according to the invention allows optimum utilization of the energy supply of the energy accumulator without running the risk that the energy supply will be exhausted before the destination is reached. This is achieved, in particular, by continuously updating the set point for driving-power limitation as the vehicle travels along, and adapting it to the actual energy supply still available and to the remaining distance ahead. This arrangement has the further advantage that it is possible to calculate the energy safety reserves more closely, which reduces the weight of the vehicle and contributes to economy.